1. Field of the Invention
The present invention relates generally to pagers, and more particularly, to a method for urging transmission of an answer message in a bilateral pager when receiving a call message.
2. Description of the Related Art
Generally, a bilateral pager has the capability of receiving a message and transmitting answer data responding to the received message, along with additional data in accordance with a user's selection. A base station exchanger transmits an answer message selected by a user to a call transmitter, forming a communication channel.
FIG. 1 is a block diagram illustrating electronics within a prior art bilateral pager. An RF receiver 11 receives a radio paging signal via an antenna 23, and performs frequency conversion and waveform shaping of the paging signal. The output of RF receiver 11 is thus a radio paging signal converted to digital data, which is then applied to a decoder 12. The decoder 12 sets an operation mode of the radio pager by decoding the digital data. In an idle mode, decoder 12 detects preamble data, and in a batch mode, it detects wordsync data and an established frame data. Also, it decodes the detected frame data to convert the same into original data.
A controller 13 utilizing a microprocessor receives decoded data from decoder 12. Controller 13 controls a call alarm function by processing the received data and generating an alarm control signal. A transmission message and related information is generated by controller 13 by first generating an address designating a particular area of memory. Controller 13 reads data from the relevant area of the memory according to a given output instruction and transfers it to a display 16. An alarm 17 generates an alarm signal such as an audible tone or vibration in response to the alarm control signal transmitted from controller 13. Display 16, typically a liquid crystal display, displays a caller's message, pager state information, and a transmission message and its transmission related information. A first memory 15 (e.g., RAM) stores the transmission message and its transmission related information. A second memory 25 (e.g., PROM) stores address and frame information allocated and peculiar to the pager.
Referring to FIG. 2, a flow chart for processing an answer message responding to a call message in a bilateral pager is shown. Controller 13 transmits an alarm control signal to alarm 17 to generate a "receipt alarm" in step 213 indicating that a page has been received. The receipt alarm is generated when a call message requiring an answer is received by the bilateral pager in step 211. (The caller may select whether or not the page requires an answer). The alarm 17 generates an alarm signal such as an audible tone or vibration selected by a key input. Information related to the call message is stored for a given time in the data base of first memory 15 when the bilateral pager is in an answer transmission mode in step 214. The bilateral pager transmits an answer message to a caller when receiving the call message. The controller 13 operates a timer in step 215.
A reverse paging system (hereinafter referred to as `RPT`) receiving the answer message from a bilateral pager of a receiving party, stores the call message related information for a given time in a database. Accordingly, the RPT transmits the answer message by forming a communication link with the caller when receiving the answer message from the bilateral pager. In the receiving party's bilateral pager and the RPT, the time allocated to store the answer message is restricted due to limited database capacity. After receiving a call, the receiving party selects a proper answer message from multiple answer messages provided previously by means of a key input 10 on the pager (FIG. 1). The selected answer message is transmitted through an RF transmitter 22.
As the timer is operated in step 215, it is determined in step 216 whether or not the above-discussed answer message has been transmitted. If no answer message has been transmitted within a certain time interval, i.e., within a predetermined "mode change time" interval (steps 216-217) the timer is initialized in step 218, and the controller enters a "no-answer transmission mode" is step 219. The RPT erases information related to the caller when no answer message is received within the mode change time. After the mode change time interval, the communication link can not be established even if the answer message is received afterwards. In other words, a bilateral pager user should transmit an answer message within the mode change time. Therefore, a problem with a conventional bidirectional pager is that it is impossible to transmit an answer message to a caller as the RPT erases information related to the caller when no answer message is transmitted within the mode change time.